Yeah, that was the first thing I thought too. The KB listing for the IC837 says 709/141 for the Piston/Pin. The Diamond 52407 listing says537 grams. They are both .990 pin pistons. Just seems like a lot of difference, almost 6 1/4 ounces? Also the KB piston online listing mentions a special ring gap for the top ring? I thought that was just on the Hypereutectic pistons...
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just make sure that you are comparing the pistons only and the weight of the pin is not included.